I have looked around and I can't seem to find what the work function for sputtered NiCr is? Ni has a work function of 5 and Cr of 4.5 so is their alloy 4.75? I would like to verify this and if anyone knows it would be much appreciated, thanks!
Hi Matthew,
The answer to this simple question is not simple at all. The WF is a surface property and it strongly depends on fine details of the surface - some of which can be challenging to measure and characterize. E.g., what is the terminating plane of the alloy? Are some of the constituents partially oxidized?
My colleague suggested a model where surface segregation/enrichment can account for WF differences and his model works well in fully miscible alloys, where you can sometimes observe that the alloy's WF is lower than that of either constituent (e.g. Fig. 5). c.f. Rothschild & Eizenberg, PRB 2010
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.81.224201
When we're not discussing solid solutions you can have different phases, each with its own WF and its own different surface sensitivities. Again, the terminating plane can have a significant effect. My coauthors and myself have shown by DFT that for Pt-Al alloys the terminating plane can have a ~0.5 eV effect on the WF. On top of that - the crystallographic orientation also plays a role and can vary the WF by >0.5 eV in this particular example.
Attached is the full text of our PRB 2012
https://www.researchgate.net/publication/258243361_Composition_and_crystallography_dependence_of_the_work_function_Experiment_and_calculations_of_Pt-Al_alloys
The crystallographic effect plays an even stronger role in bcc metals, c.f. G. Xu et al., JAP 2009 (and other works by this author)
http://scitation.aip.org/content/aip/journal/jap/106/4/10.1063/1.3204976
Having said ALL that, sometimes the naive Vegard-like approach for the alloy's WF just happen to empirically work, as was shown experimentally in the Pt-Al cited above (Fig. 6, second link).
Data Composition and crystallography dependence of the work funct...
You can measure the work function of a material using Auger Electron Spectroscopy. No modeling needed and you can get the value for the exact material you are interested in.
Hi Matthew,
Knowing the EWF of Ni and Cr on one hand, and the atomic (or massic) proportion x for these two metals on the other hand, it is possible to calculate the EWF of the binary alloy NixCr1-x, by using the formula proposed by Gelatt and Ehrenreich:
Φ(NixCr1-x) = x*Φ(Ni)+(1-x)* Φ(Cr).
I have measured the EWF for AgMe binary alloys, e.g.AgNi(60/40), AgNi(70/30) and AgW(50/50), the numbers between brackets are the massic proportions for silver and metal, respectively. The EWF calculated values were identical to the experimental measurements, with a good accuracy.
You can take a look to the following links
Article Effects of surface treatments on photoelectric work function...
Article Effects of vacuum heat treatment on the photoelectric work f...
Besides, you can take a look to the following file (Gelatt and Ehrenreich paper).
Hi Matthew, In addition to the above suggest solutions you may also try UPS (ultraviolet photoelectron spectroscopy) to calculate the workfunction of the NiCr composite.
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